Water activity is a critical food stability parameter. Thus, assessment of the uncertainty associated with
the instruments and measurement procedures used to obtain a
w data is critical and can be accomplished
using uncertainty analysis. Uncertainty analysis was applied to a
w data obtained for two saturated salt
slurries (potassium acetate and potassium chloride) and two food materials (corn flakes and grape
jam) at 25 C using a commercially available dew point hygrometer, the AquaLab 3TE. Sources of uncertainty investigated included sample and dew point temperatures, sample lot, cup volume, and sample
preparation (‘‘as is” or ground), and day to day changes. Uncertainty analysis revealed that the magnitude
of the different sources of uncertainty depended on material type, but that the dew point hygrometer
instrument uncertainty was always significantly smaller than each of the other sources of uncertainty
investigated, except for jam cup volume, which was exceeding small. Uncertainty analysis also revealed
that dew point hygrometer accuracy was better than the ±0.003 a
w value reported by the manufacturer.
Measurement procedures were identified that could be implemented to reduce a
w
measurement uncertainty for corn flake and jam food materials. The uncertainty analysis used herein can also be applied to
investigate other food materials and/or instrument
Water activity is a critical food stability parameter. Thus, assessment of the uncertainty associated withthe instruments and measurement procedures used to obtain aw data is critical and can be accomplishedusing uncertainty analysis. Uncertainty analysis was applied to aw data obtained for two saturated saltslurries (potassium acetate and potassium chloride) and two food materials (corn flakes and grapejam) at 25 C using a commercially available dew point hygrometer, the AquaLab 3TE. Sources of uncertainty investigated included sample and dew point temperatures, sample lot, cup volume, and samplepreparation (‘‘as is” or ground), and day to day changes. Uncertainty analysis revealed that the magnitudeof the different sources of uncertainty depended on material type, but that the dew point hygrometerinstrument uncertainty was always significantly smaller than each of the other sources of uncertaintyinvestigated, except for jam cup volume, which was exceeding small. Uncertainty analysis also revealedthat dew point hygrometer accuracy was better than the ±0.003 aw value reported by the manufacturer.Measurement procedures were identified that could be implemented to reduce awmeasurement uncertainty for corn flake and jam food materials. The uncertainty analysis used herein can also be applied toinvestigate other food materials and/or instrument
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